This can let us create versions of skia_public with certain settings
enabled in an easy way (i.e. not requiring clients to set the compile
flags themselves).
Change-Id: I909449c6186f4912ea80dd9d579fcd7cafb4775c
Bug: skia:12541 b/237076898
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/553377
Reviewed-by: Jorge Betancourt <jmbetancourt@google.com>
